gala (n.)

1620s, "festive dress or attire" (obsolete), from French en gala, perhaps from Old French gale "merriment," from galer "rejoice, make merry" (see gallant). Klein suggests the French word is from Italian gala (as in phrase vestito di gala "robe of state"), perhaps from Arabic khil'a "fine garment given as a presentation." Sense of "festive occasion" (characterized by display of finery) first recorded 1777. Quasi-adjectival use in gala day "day of festivities," etc.